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([2600:8803:e7e4:1d00:d77b:6acc:2ad1:8ff]) by smtp.gmail.com with ESMTPSA id 586e51a60fabf-2e3c0b2c853sm2681647fac.50.2025.05.21.08.05.56 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 21 May 2025 08:05:57 -0700 (PDT) Message-ID: Date: Wed, 21 May 2025 10:05:56 -0500 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 3/3] pwm: axi-pwmgen: add support for external clock To: =?UTF-8?Q?Nuno_S=C3=A1?= , =?UTF-8?Q?Uwe_Kleine-K=C3=B6nig?= Cc: Michael Hennerich , =?UTF-8?Q?Nuno_S=C3=A1?= , Trevor Gamblin , Rob Herring , Krzysztof Kozlowski , Conor Dooley , linux-pwm@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org References: <20250520-pwm-axi-pwmgen-add-external-clock-v1-0-6cd63cc001c8@baylibre.com> <20250520-pwm-axi-pwmgen-add-external-clock-v1-3-6cd63cc001c8@baylibre.com> <0dd1a97e-ff7c-4d09-b18e-5df9944488c6@baylibre.com> <6b72e9dc9d574aa1f025c0f5d317dcec1d729ba9.camel@gmail.com> Content-Language: en-US From: David Lechner In-Reply-To: <6b72e9dc9d574aa1f025c0f5d317dcec1d729ba9.camel@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 5/21/25 9:22 AM, Nuno Sá wrote: > On Wed, 2025-05-21 at 15:54 +0200, Uwe Kleine-König wrote: >> Hello David, >> >> On Wed, May 21, 2025 at 08:19:51AM -0500, David Lechner wrote: >>> On 5/21/25 4:22 AM, Uwe Kleine-König wrote: >>>> Can you achieve the same effect with the (IMHO slightly nicer but >>>> hand-crafted) following patch: >>>> >>>>   ddata = pwmchip_get_drvdata(chip); >>>>   ddata->regmap = regmap; >>>>   >>>> - clk = devm_clk_get_enabled(dev, NULL); >>>> - if (IS_ERR(clk)) >>>> - return dev_err_probe(dev, PTR_ERR(clk), "failed to get >>>> clock\n"); >>>> + axi_clk = devm_clk_get_enabled(dev, "axi"); >>>> + if (IS_ERR(axi_clk)) >>>> + return dev_err_probe(dev, PTR_ERR(axi_clk), "failed to >>>> get axi clock\n"); >>>> >>>> + clk = devm_clk_get_enabled_optional(dev, "ext"); >>>> + if (IS_ERR(clk)) >>>> + return dev_err_probe(dev, PTR_ERR(clk), "failed to get >>>> ext clock\n"); >>>> + } >>> >>> The trouble with this is that it would not work with existing .dtbs >>> that don't have clock-names set. I think it would need to be more like this: >>> >>> >>> axi_clk = devm_clk_get_enabled(dev, NULL); >>> if (IS_ERR(axi_clk)) >>> return dev_err_probe(dev, PTR_ERR(axi_clk), "failed to get >>> axi clock\n"); >>> >>> clk = devm_clk_get_enabled_optional(dev, "ext"); >>> if (IS_ERR(clk)) >>> return dev_err_probe(dev, PTR_ERR(clk), "failed to get ext >>> clock\n"); >>> >>> if (!clk) >>> clk = axi_clk >>> >> >> If there are no clock-names, the parameter is ignored. (I didn't test, >> only quickly checked the code.) So passing "axi" instead of NULL should >> work and yield a more robust solution. >> >> > > Are you sure? If there are no clock-names and you pass an id, you should get an > error back: > > https://elixir.bootlin.com/linux/v6.14.7/source/drivers/clk/clk.c#L5198 > > > I know it's not exactly the same we're discussing but of_property_match_string() > return -EINVAL if the property is not found which leads to an index < 0 and thus > of_parse_phandle_with_args() also returns an error back. > > I think I'm not missing anything but it's always a possibility. > > - Nuno Sá Testing agrees: Given: clocks = <&some_clock>; /delete-property/clock-names; And: axi_clk = devm_clk_get_enabled(dev, "axi"); We get: [ 1.190040] axi-pwmgen 44b00000.pwm: error -ENOENT: failed to get axi clock